Odor-masking coating for a pharmaceutical preparation

ABSTRACT

A coating for masking or reducing the detectable presence of certain characteristic odor or odors, taste or tastes of pharmaceutical preparations, particularly Valerian extracts, is described. The coating comprises from one to three coating compartments, in any combination or as a single-layer amalgam. The first coating compartment comprises a hydroxyalkyl cellulose and an anti-tackiness agent The second coating compartment may comprise a sugar and at least one anti-tackiness agent. The third coating compartment may comprise a methacrylate copolymer, a hydroxyalkyl cellulose and an anti-tackiness agent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to tablet coatings. Moreparticularly, the invention relates to a coating useful in masking theodor of pharmaceutical preparations, particularly extracts from theplant Valerian.

2. Description of the Related Art

Pharmaceutical preparations are sometimes associated with unpleasantodors. For example, the strong, unique, unpleasant, and characteristicodor of extracts of the root of the plant Valeriana officinalis L. arewell known.

Methods are known for masking such odors. For example, and mosttypically, flavoring agents may be added to a medicaments (e.g., apharmaceutical or other formulation) to change the taste of oralmedications. Alternative methods to change the smell or taste ofmedicaments are available, such as smell masking or taste masking. Oneof the common goals of these various methods of taste and smell maskingis to make the medication more appealing to consumers. This goal maylead to an increase in consumer compliance with prescribed and/orrecommended dosing regimens.

Extracts of the root of the plant Valeriana officinalis L. (V.officinalis L.) have been used for medicinal purposes for over acentury. Certain valerian extracts, including aqueous extracts, areknown to have sedative and anxiolytic effects, but the active componentshave not been clearly and positively identified. See Leathwood P. D.,and Behavior, 17:65-71 (1982); Leathwood P. D. and Chauffard F.,“Aqueous extract of valerian reduces latency to fall asleep in man,”Planta Medica, 2:144-148 (1985). Such effects are described by Balandrinet al. in U.S. Pat. No. 5,506,268, which is incorporated by referenceherein in its entirety. Presently, valerian is available as dietarysupplements; these dietary supplements primarily comprise dried root orextracts from the root, formulated into tablets or gelatin capsules.Each dose contains between approximately 50 mg and approximately 1 gramof dried root or extract.

It is not known in the art which constituents of Valeriana officinalisL., and/or of the other heretofore unidentified members of theValerianaceae family, are responsible for the sedative and/or anxiolyticaction of valerian extracts. Nonetheless, the valepotriates (iridoids)as well as valerenic acid, a sesquiterpenoid compound, and thederivatives of valerenic acid (for example, acetoxyvalerenic acid andhydroxyvalerenic acid) along with the kessane derivatives, valeranone,valerenal, and certain amino acids are present in valerian extracts. Ofthese components, the valepotriates and valerenic acids are generallyconsidered to contribute to the sedative action of valerian extracts,but have not been clearly and positively identified as such. SeeHendriks H. et al., “Pharmacological Screening of valerenal and someother components of essential oil of Valeriana officinalis,” PlantaMedica, 42, 62-68 (1981); Bos R. et al., “Analytical aspects ofphytotherapeutic valerian” (1996); Houghton P. J., Valerian. The GenusValeriana. Harwood Academic Publishers, London. (1997).

The therapeutic benefits of extracts of the root of the plant Valerianaofficinalis L. are well-known, and are described in the literature. Suchextracts do have a strong, identifying, characteristic and unpleasantsmell or odor and an associated disagreeable taste. This characteristicodor and/or this characteristic taste make consuming sufficienttherapeutic quantities of the extracts of the root of the plantValeriana officinalis L. difficult for a substantial percentage of thepopulation. In one reported effort to mask the smell of an extract ofthe root of a plant of the genus Valeriana, see U.S. Pat. No. 5,211,948to Cerise et al., the degradation products of valepotriates areidentified as the odor causing agents in the aqueous extraction ofValerian root. This reference describes that the odors may be eliminatedby, for example, the steps of concentrating the aqueous extract andprecipitating the resultant extract with acetone. The precipitatedcomponents may then be removed from the rest of the extract viacentrifugation. The reference describes that the valerenic acids foundin the roots remain present in the resulting extract, and that theresulting extract has a neutral taste and smell. However, as alsodescribed in U.S. patent application Ser. No. 60/173,983, entitled“Process For Reducing The Odor Of Valeriana,” and filed on this date andherewith, the disclosure of which is hereby incorporated by referenceherein, (1) when an aqueous extract of Valerian root was producedaccording to a method of the '948 patent, it was observed that theextract still contained the significant, distinctive, characteristic andpungent smell and associated taste of Valeriana, (2) inconsistent withthe teachings of U.S. Pat. No. 5,211,948 to Cerise et al., thecharacteristic odor of V. officinalis extract may be significantlyreduced via the addition of a sufficient amount of a chemical base tothe extract formulation, and (3) the addition of base reduces thepungent smell by lowering the vapor pressure of isovaleric acids, andother like acidic components of a V. officinalis extract, which aretherefore the source of the characteristic odor and taste.

Certain conventional approaches for masking odors of medicinalpreparations, especially tablets, also utilize sugar-coating technology.Such conventional technology typically requires the use of anon-perforated coating pan and generally requires extensive materials,long processing times, multiple stages/layers, and experiencedscientists to obtain products with acceptable quality, i.e. odor maskingand smooth appearance. Sugar-coating technology has been applied to thecommercially available valerian tablet product, Sedonium®, manufacturedby Lichtwer Pharma AG, Berlin, Germany. In this product, the weight ofthe sugar coat applied to each tablet is nearly a half of the coretablet weight.

In the pharmaceutical industry, an alternative coating technique,applicable to tablets, film coating, is generally performed in aperforated coating pan or fluid-bed particle coater. The benefits offilm coating, with respect to sugar coating, include: (1) shortenedprocessing time; (2) substantially reduced coating material quantity;(3) easily controlled processing conditions; (4) improvedreproducibility from small scale to large scale; and (5) increasedselection options for coating materials or polymers.

There is a need in the art for an alternative coating capable of maskingodors of various pharmaceutical preparations. The present inventionaddresses this need, among others.

SUMMARY OF THE INVENTION

A pharmaceutically-inert coating is described that is effective inmasking the characteristic, unpleasant odor (and/or taste) of a plant orplant extract, and particularly of the root or an extract of the root ofthe plant Valerian. The coating comprises one or more of the followingcoating compartments: a first coating compartment comprising ahydroxyalkyl cellulose and an anti-tackiness agent and, optionally, aplasticizer; a second coating compartment comprising a sugar and atleast one anti-tackiness agent; and a third coating compartmentcomprising a methacrylate copolymer, a hydroxyalkyl cellulose and ananti-tackiness agent. The hydroxyalkyl cellulose of the first coatingcompartment is preferably selected from the group consisting ofhydroxyethyl cellulose and hydroxypropyl cellulose. The anti-tackinessagent of the first coating being preferably selected from the groupconsisting of talc, silicon dioxide, silica hydrogel, microcrystallinecellulose, alkali stearates, and starch. The second coating compartmentpreferably also comprises a plasticizer; the plasticizer beingpreferably selected from the group consisting of propylene glycol,glycerin, trimethylolpropane, polyethylene glycols, dibutyl sebacate,acetylated monoglycerides, diethylphthalate, triacetin, glyceryltriacetate, acetyltriethyl citrate and triethyl citrate. The thirdcoating compartment may also comprise a plasticizer; the plasticizerbeing preferably selected from the group consisting of propylene glycol,glycerin, trimethylolpropane, polyethylene glycols, dibutyl sebacate,acetylated monoglycerides, diethylphthalate, triacetin, glyceryltriacetate, acetyltriethyl citrate and triethyl citrate; and the thirdcompartment may also comprise a water soluble polymer, preferably beingselected from the group consisting of hydroxypropyl cellulose,hydroxypropyl methylcellulose, acacia, sodium carboxymethylcellulose,dextrin, alginic acid, ethylcellulose resin, gelatin, guar gum, liquidglucose, methylcellulose, pregelatinized starch, sodium alginate,starch, zein, polyvinylpyrrolindone, vinylpyrrolidone-vinyl acetatecopolymer, vinyl acetate-crotonic acid copolymer and ethylacrylate-methacrylic acid copolymer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form part ofthe specification, merely illustrate embodiments of the presentinvention. Together with the remainder of the specification, they aremeant to serve to explain the principles of the invention to those ofskill in the art. In the drawings:

FIG. 1 depicts a cross-sectional view of a preferred embodiment of themultilayer odor-masking coating of the present invention. A tabletdosage form is shown as an example, and the pharmaceutically activetablet core, 2, is cross-hatched.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a coating for masking the odor ofpharmaceutical preparations. Although the masking of odor from valerianextracts is described herein, the coating and coating methods of thepresent invention may be applied to any pharmaceutical formulation intablet or capsule form which has a strong or unpleasant odor.

The method described in the present application uses film coatingtechnology. This method provides an advantage of allowing for the use ofa reduced amount of coating materials and the advantage of improvedodor-masking efficiency when compared to commercially available Valeriantablets. According to the present invention, odor reduction may beachieved with a coating material amount of about, for example, 25% orless of the core tablet weight, compared to the about 50% forcommercially available products.

As used herein, the terms “Valeriana” and “Valerian” refer to any plantof the Valerianaceae, and therefore refers, at least to, the plantdesignated Valeriana officinalis L. This species includes all recognizedsubspecies of Valeriana officinalis L. Some of these subspecies are alsocommonly referred to, in alternative taxonomic systems, as: Valerianaexaltata J. C. Mikan, Valeriana nitida Kreyer, Valeriana palustrisWibel, Valeriana wolgenis Kazak, Valeriana grossheimii Vorosch,Valeriana collina Wallr, Valeriana Rossica P. A. Smirn, Valerianaspryngini P. S. Smirn, Valeriana angustifolia Tausch, Valerianatenuifolia Vahl, Valeriana wallrothii Kreyer, Valeriana ucrainicaDemjan, Valeriana sambucifolia J. C. Mikan, Valeriana excelsa Poir, andValeriana officinalis L.subsp. excelsa (Poir.) Rouy. Plants of thespecies Valeriana officinalis L. may be characterized as follows: Theseplants grow from a short rhizome to 2 m high, flowers, and then die backagain in the winter. These plants have pinnately-divided leaves with sixto ten pairs of lance-shaped leaflets, and bear many small white or pinkflowers in a dense head of several stalked clusters. The heads baresmall (5 mm) tapered seeds.

As used herein, the terms “reduces,” “reduced,” or “reducing,” when usedto refer to a particular odor or taste characteristic, refers to anyobservable lessening of that characteristic when the method orcomposition of the present invention is compared to prior art methods orcompositions.

As used herein, the term “roof” or “roots” refers to all of subterraneanportion of a specifically or generically identified plant, including,but not limited to, the roots, the rhizomes, and the stolons of thespecifically or generically identified plant. Where the term “roots” isnot modified by a specifically or generically identified plant, it willbe understood that the term refers to the roots of the species, and tosub-species of, Valeriana officinalis L.

As used herein, the terms “odor,” “smell,” and “scent” refer toolfactory recognition of any particular or group of particular gases.Preferably, the olfactory recognition refers to mammalian, and mostpreferably human, olfactory recognition. Such recognition was determinedby observation by the inventors, and may alternatively be determined bya cross-section of the population or by quantitative or qualitativerecognition devices known to those of skill in the art.

With reference to a preferred embodiment, as depicted in FIG. 1, each ofthe three inner coating compartments can be applied alone or incombination with other layers to mask the odor of the core tablet. Inother words, the coating of the invention may comprise one, two or allthree of the three inner layers, in any combination or in any order orarrangement. The sequence of coating layer application can be altered toaccommodate product or manufacturing needs. An optional cosmetic colorcoat, which need not have an odor-masking effect, may be applied as aseparate layer or combined in one or more of the polymer layer orlayers. Pharmaceutical coatings are described in detail by Bauer et al.in Coated Pharmaceutical Dosage Forms: Fundamentals, ManufacturingTechniques, Biopharmaceutical Aspects, Test Methods and Raw Materials,CRC Press, Boca Raton, Fla., 1998.

BRIEF DESCRIPTION OF THE DRAWING

The coating compartments of a preferred embodiment of the presentinvention are shown schematically in FIG. 1. Tablet core 2, and crosshatched, with reference to FIG. 1, is coated with first coatingcompartment 4 which preferably comprises a hydroxyalkyl cellulose inwhich the alkyl group has between one and ten carbon atoms, and ananti-tackiness agent. The hydroxyalkyl cellulose functions as one ormore of the following: film former, coating agent, suspending agent,tablet excipient, demulcent and viscosity-enhancing agent. Thesehydroxyalkyl celluloses include, but are not limited to, hydroxypropylcellulose, hydroxymethyl cellulose and hydroxyethyl cellulose.Hydroxypropyl cellulose is a non-ionic, water-soluble polymer and isused in films and coatings due to its excellent film flexibility,toughness, and barrier to oil and fat. Hydroxyethyl cellulose is anon-ionic, water-soluble polymer, which has been used to form matrixtablets to obtain desired modified release properties. Either or both ofthese polymers may be incorporated into the first coating compartment.Hydroxypropyl cellulose includes, but is not limited to, various gradesof Klucel® (Hercules, Aqualon Division). Hydroxyethyl celluloseincludes, but is not limited to, various grades of Natrosol® (Hercules,Aqualon Division). In a preferred embodiment, the amount of hydroxyalkylcellulose in the first coating compartment is between about 10-70% w/w.

Anti-tackiness agents reduce the tackiness (stickiness) of thepharmaceutical preparations. These agents include, but are not limitedto, talc, silicon dioxide, silica hydrogel, microcrystalline cellulose,alkali stearates, and starch. In a preferred embodiment, the amount ofanti-tackiness agent in the first coating compartment is between about20%-60% w/w.

Optionally, a compound which facilitates the coating process is added.Many such compounds are known in the art and include ethylcellulose,methylcellulose and carboxymethyl ethylcellulose. A preferred additiveis hydroxypropyl methylcellulose. Types of hydroxymethyl celluloseinclude, but are not limited to, various grades of Methocel® (e.g.,Methocel A, E, F, and K; Dow Chemical, Midland, Mich.), Pharmacoat®(e.g., Pharmacoat 606, 603, 615, and 904) (Shin-Etsu Chemical Co., Ltd.,Japan/Dynamix Cosmo Private Ltd., Singapore), and Metolose SM (Shin-EtsuChemical Co., Ltd., Japan/Dynamix Cosmo Private Ltd., Singapore). In apreferred embodiment, the coating process-facilitating compound is addedin an amount of up to 20% w/w.

Optionally, a plasticizer may be incorporated into the first coatingcompartment Plasticizers are compounds which impart flexibility,workability or stretchability to the coating. Plasticizers include, butare not limited to, propylene glycol, glycerin, trimethylolpropane,polyethylene glycols, dibutyl sebacate, acetylated monoglycerides,diethyl phthalate, triacetin, glyceryl triacetate, acetyltriethylcitrate, and triethyl citrate. In a preferred embodiment, theplasticizer is added in an amount of up to 20% w/w.

The second coating compartment 6 comprises a sugar and one or moreanti-tackiness agents Sugars increase the palatability of thepreparation. Suitable sugars for incorporation into the second coatingcompartment 6 include, but are not limited to, sucrose, dextrose,dextrin, maltose, glucose, fructose, mannose, sorbitol, lactose,mannitol, xylose and the like. The amount of sugar incorporated into thesecond coating compartment is generally about 20-80% w/w. The amount ofanti-tackiness agent incorporated into the second coating compartment isgenerally about 5-50%. In a preferred embodiment, two anti-tackinessagents are used, one of which is either talc or silicon dioxide.Preferably silicon dioxide is one of anti-tackiness agents in a sugarsystem such as that of the preferred embodiment of the second coatingcompartment described herein.

Optionally, one of the following additives may be incorporated into thesecond coating compartment to facilitate the coating process: polyvinylpyrrolidone, vinylpyrrolidone acetate copolymer, vinyl acetate-crotonicacid copolymer, ethyl acrylate-methacrylic acid copolymer, hydroxypropylcellulose, gelatin, acacia, or other cellulose derivatives. Theseadditives are generally added in an amount of about 0-30% w/w.Optionally, a plasticizer may be incorporated into the second coatingcompartment. The amount of plasticizer is typically about 0-20% w/w.

The third coating compartment 8 comprises a polymethacrylate, ahydroxyalkyl cellulose in which the alkyl group has between one and tencarbon atoms, and an anti-tackiness agent. Polymethacrylates include,but are not limited to, methacrylic acid/methyl methacrylate copolymers,methacrylic acid/ethylacrylate copolymers aminoalkylmethacrylatecopolymers, and ammoniomethacrylate copolymers. In general, the amountof methacrylate copolymer incorporated into the third coatingcompartment is between about 1-30% w/w and the amount of hydroxyalkylcellulose is between about 5 and 70% w/w.

Methacrylate copolymers are water-insoluble, and will hydrate and swellin the presence of water. Eudragit NE30D (Rohm) is one example of thisseries of polymers and is an aqueous dispersion of a neutral copolymercontaining ethyl acrylate and methyl methacrylate. This series ofpolymers is widely used in functional coatings to achieve delayed orcontrolled release of a pharmaceutical agent. In some cases, these typesof polymers are used in matrix tablets due to their modified drugrelease properties. These polymers can be used alone or in combinationwith one or more other members of the series.

Optionally, a compound which facilitates the coating process is added. Apreferred additive is hydroxypropyl methylcellulose. A plasticizer mayalso be added. The preferred amount of each of these compounds to beincorporated into the third coating compartment is between about 0-20%w/w.

In another preferred embodiment, water-soluble, non-Eudragit typepolymers or compounds are combined with Eudragit type (methacrylic)polymers to achieve odor masking without prolonged drug release. Suchwater-soluble polymers or compounds include, but are not limited to,hydroxypropyl cellulose, hydroxypropyl methylcellulose, acacia, sodiumcarboxymethylcellulose, dextrin, alginic acid, ethylcellulose resin,gelatin, guar gum, liquid glucose, methylcellulose, pregelatinizedstarch, sodium alginate, starch, zein, polyvinylpyrrolindone,vinylpyrrolidonevinyl acetate copolymer, vinyl acetate-crotonic acidcopolymer, and ethyl acrylate-methacrylic acid copolymer. The percentageof selected chemicals in the film may vary widely depending on thenature of selected material. Plasticizer may be included if necessary toimprove the flexibility and appearance of the film.

Optionally, a fourth coating compartment 10 may be applied as a cosmeticcolor coat which need not function as an odor-masking coat. Optionally,the color coat may be combined with one of the other three coatingcompartments. In one embodiment, the color coat is Opadry II (32K11498), Green (®, Colorcon inc.). Alternative components for the colorcoat, and the selection of same, are within the skill of those in theart.

Other ingredients such as lubricants, color pigments, surfactants,glidants, etc. may be included in one or more of the coatingcompartments to assist coating operation and/or improve film quality.The selection of such alternative ingredients is within the skill ofthose in the art. Lubricants may include, but not limited to, calciumstearate, hydrogenated vegetable oils, magnesium stearate, mineral oil,polyethylene glycols, stearic acid, sodium benzoate, sodium laurylsulfate, leucine, and sodium stearyl fumarate. The percentage of totalsolids in a preferred selected solvent or solvent mixture may be in therange of about 5% to 50% w/w, and preferably about 8-12% w/w.

All of the coating layers described herein can be applied usingconventional film coating technology well known in the pharmaceuticalindustr. See, for example, Remington's Pharmaceutical Sciences (A. R.Gennaro edit. 1985), Mack Publishing Co, Easton, Pa. For example, filmcoating may be performed in a perforated coating pan or fluid-bedparticle coater. Each coating layer may be applied to either tablet ormultiparticular medicinal preparations. Depending on the nature of theselected coating materials, the following solvents, whether used aloneor in combination, may be used to prepare coating solution orsuspension: water, ethanol, methanol, acetone, isopropyl alcohol, aceticacid, glycerin, and methylene chloride, etc. Examples of coatingmaterials contemplated for use in the present invention is presented inthe examples.

As described above, the conventional sugar-coating process typicallyinvolves the use of a traditional non-perforated coating pan. With thepresence of proper additives such as auxiliary film formers,anti-tackiness agents, and/or water insoluble fillers as described inthe present invention, acceptable sugar film can be achieved using aperforated coating pan or fluid-bed particle coater.

Either a perforated coating pan or a fluid-bed particle coater may beemployed to apply coating materials, as described above, to medicinalpreparations containing extracts from the plant Valerian. A preferredprocess for the extraction of Valerian root is described in copendingU.S. patent application Ser. No. 09/358,375, filed Jul. 21, 1999, andentitled “Process for the Extraction of Valerian Root” the entirecontents of which are incorporated herein by reference. These extractscomprise essential oils, valerenic acids, kessane derivatives,valeranone, valerenal, fatty acids, carbohydrates and certain aminoacids, and may, depending on the extraction condictions, includevalepotriates (iridoids).

The valerian root extraction process for the preparation of thepharmaceutically active tablet core 2 component of tablets of thepresent invention, may involve heating a mixture of the roots and analcoholic extraction solvent for an extended period of time to obtainvalerenic acid and valerenic acid derivatives in the extract, and tosignificantly reduce the amount of valepotriates in the extract. Thisextraction process, as described in co-pending U.S. patent applicationSer. No. 09/358,375, which is hereby incorporated by reference, whencompared to currently available processes, significantly reduces theamount of valepotriates in the valerian extract, while maximizing theamount of valerenic acid and of valerenic acid derivatives.

The process of preparing a formulation of the present inventiontherefore may include an extraction process. The complete process forpreparing such a formulation is described to place the extractionprocess in the context of the preparation of the pharmaceutically activeformulation and the coating and coating methods of the presentinvention. The following five steps comprise the process for preparingsuch a formulation: Pre-Extraction Processing of the Root, Extraction,Drying and Milling of the Drug Substance, and Formulation of a Tablet orCapsule. Additional or alternative steps, as well as the use ofdifferent pharmaceutical formulations, may be added without departingfrom this process.

Pre-Extract Processing of the Root. The roots may be prepared forextraction by grinding, chipping, or pulverizing to a powder in ahammermill, or a like instrument, as will be appreciated by those ofskill in the art. After such pre-extraction processing, preferably atleast 70%, 75%, or 80%, and most preferably 85% or 90% of the mass ofthe roots pass through a Tyler 20-mesh screen. Also preferably, the rawor processed roots are stored in a durable non-reactive, preferablyplastic, and more preferably polyethylene, container or containers.These containers may be doubly-lined with bags of like material andclosed or closeable with a lid composed of like material.

Extraction. The valerian root, whether, as preferred, processed asdescribed above or in an unprocessed state, may be added to anextraction solvent. Most preferably, the root is added in a ratio ofapproximately one kilogram to approximately five liters of extractionsolution. The extraction solvent preferably is an alcoholic extractionsolution, comprising between approximately 30% to approximately 100%(volume/volume; v/v) alcohol and between approximately 70%(volume/volume; v/v) to 0% (v/v) water. Preferably, the alcoholicextraction solvent comprises approximately 50% to approximately 100%(v/v), approximately 55% to approximately 95% (v/v), approximately 65%to approximately 85% (v/v), and approximately 65% to approximately 75%(v/v) alcohol. Specifically, the alcoholic extraction solvent maycomprise approximately 50% (v/v), approximately 60% (v/v), approximately70% (v/v), approximately 80% (v/v), approximately 90% (v/v) alcohol andapproximately 100% alcohol. The alcohol used in the alcoholic extractionsolvent is fully miscible in water, and is preferably denatured ethanol(95% ethanol+5% methanol), but may be any C₁-C₆ alcohol, including butnot limited to methanol, ethanol, n-butanol, isobutanol, n-propylalcohol, and isopropyl alcohol.

The mixture of root and alcoholic extraction solvent may be stirred byany mechanical device conventionally known for such purpose, includingbut not limited to an overhead stirrer, a magnetic stirrer assembly,and/or a built-in stirrer, and may be suitable for or adapted to theparticular extraction vessel employed. The mixture may be heated tobetween approximately 65° C. and 85° C., and more preferably betweenapproximately 70° C. and 80° C., or alternatively, the temperature ofreflux. Specifically, the mixture may be heated to 50°, 55°, 60°, 65°,70°, 75°, 77°, or 80° or reflux. Various conventional methods may beused to heat the mixture, including but not limited to heating mantelsor other resistive heating coils.

Preferably, the mixture is heated to any of the above-describedtemperature for at least one, one and one-half, two, two and one-half,three, three and one-half hours, four, or up to five hours. Thesedurations, most preferably the latter three durations, are selected tosignificantly reduce the level of valepotriates relative to the initialvalue, preferably at least a 50% reduction. (Final Value/InitialValue=Percent Reduction). More preferably the reduction is by 60%, 70%,75%, 80%, 90%, 95%, and most preferably 100% of the detectable level ofvalepotriates. In the latter case, the valepotriate level is notdetectable by conventional techniques. The final valepotriate level maybe obtained and may also be compared to that found in commercialvalerian extracts.

Optionally, the mixture may then be cooled, preferably to roomtemperature or alternatively to a temperature above room temperature,including 30° C., 35° C., 40° C., 45° C., and 50° C. The solids may thenbe separated from the liquid (by filtration or centrifugation or anyother conventional method for separation). The extraction vessel and theseparated solids may be rinsed with the extraction solvent, describedabove. For such a rinse, from approximately four liters, three liters,two liters, or preferably one liter of extraction solvent may be usedfor each kilogram of root initially extracted.

Also optionally, the filtrate containing the extracted material may beconcentrated to an oily consistency under reduced pressure, includingapproximately 0.9, 0.8, 0.7, 0.6, and 0.5 atms, at a temperature aboveroom temperature, including 30° C., 35° C., 40° C., 45° C., and 50° C.Optimally, a final volume of approximately 0.15 liters for each kilogramof root extracted is obtained.

Addition of Excipient to facilitate drying. The concentrate may be mixedwith an excipient to facilitate drying. The excipient may be chosen fromany commercially-available excipient or mixtures thereof, but ispreferably selected from the following: Maltodextrin, NF, TricalciumPhosphate, and Silicon Dioxide or other conventional excipient and anycombination or mixture thereof as will be recognized by those of skillin the art. After addition of the excipient, the excipient willpreferably comprise between approximately 10% and 40%, and morepreferably between 20% and 25%, of the drug substance.

Drying and Milling of the Drug Substance. The concentrated valerianextract and excipient, if added, is dried under reduced pressure,including approximately 0.9, 0.8, 0.7, 0.6, and 0.5 atms, at atemperature slightly above room temperature, including 30° C., 35° C.,40° C., 45° C., and 50° C. Optimally, the drying is continuous untilwater content is equal to or less than 15%, 10%, or 5%, as measured byKarl Fischer analysis. The dried mixture may then be milled to a targetof 80%, 85%, 90%, or 95% by weight passing through a size-exclusionscreen of 60-mesh, 70-mesh, 80-mesh, 90-mesh, or 100-mesh.

Optionally drying of the extract may be accomplished by spray drying orany other conventional drying method as will be understood by one ofordinary skill in the art.

In a preferred embodiment, the dried extract is then formulated into acore for use as a tablet core having a pharmaceutical dosage form suchas crystals, granules, pellets, tablets, and hard and soft gelatincapsules using convention methodology well known in the pharmaceuticalarts. See, for example, Remington's Pharmaceutical Sciences (A. R.Gennaro edit. 1985), Mack Publishing Co, Easton, Pa., or latest edition.In a preferred embodiment, the dosage form is a tablet. Tablets areformed using one or more of the following: excipients which aid in thetableting process, glidants, binders, disintegrants, fillers, diluentsand lubricants.

The application of coating compartments of the present invention toValerian tablet core using a perforated coating pan is described below.Each coating layer may be applied to Valerian tablets utilizing thecommonly used perforated coating pan system equipped with the spraynozzle assembly. Core (uncoated) tablets are placed inside the coatingpan and the coating pan is rotated at a selected speed to providemovement of the tablets. A pump device is used to deliver coatingsolution or suspension at a selected rate to the spray nozzle assembly.With the presence of compressed air through the spray nozzle assembly,coating solution or suspension is atomized into small droplets or mistswhen coming out from the nozzle tip. Airflow pre-heated to the desiredtemperature and controlled at the desired flow rate is applied to thetablets throughout the coating run to assist evaporation of the coatingsolvent(s). The evaporation of coating solvent(s) causes solids incoating solution or suspension to deposit on the tablet surface and formthe protective film or layer around the tablets. Cleaning of the productcontact surface inside the coating pan within or between coating layersmay be required to minimize contact of odor carrying materials from pansurface to coated tablet surface.

Odor-masking efficiency can be verified easily by comparing the smell oftablets before and after coating. The presence of a strong, unique, andunpleasant odor is a very specific characteristic of the uncoatedtablets containing Valerian extracts. Tablet samples before and afterodor-masking coating may also be separately packaged into high densitypolyethylene bottles, sealed, and stored at room temperature for apre-determined time period. The odor between coated and uncoated tabletscan be compared by smelling the samples immediately after opening thesealed bottles.

The benefits of the odor-masking system described herein include, butare not limited to:

1. The complicated multiple-stage coating process employed fortraditional sugar-coating operation may be eliminated or substantiallysimplified. For example, this odor-masking technique of the presentinvention does not need to incorporate sealing coat polishing layer, andgross coat as typically required in sugar coating.

2. Each layer may be applied in various combination or sequence or evena single layer with slight modification in applied amount.

3. The coating system and operation technique are widely used inpharmaceutical industry. No special training or parts are required.

4. Proposed coating materials are commonly used in pharmaceuticalindustry and can be substituted with other similar compounds in the samechemical group.

5. Coating amount can be easily controlled or modified to achieve thedesired odor-masking criteria.

The extract produced, and preferably the tablets produced according tothe methods of the present invention advantageously may be administeredto an individual in a dose containing a pharmaceutically-effectiveamount of Valerian, Valerian extract, or component(s) therein. Thisadministration can be through any effective route. It is contemplatedthat administration may be effected, for example, preferably orally, butalso may also be administered intramuscularly, subcutaneously,intraperitoneally, transdermally, transmucosally, buccally, or throughinhalation or pulmonary infusion. Dosages that are contemplated for a 70kg adult human range from a lower limit of 10, 25, 50, 100, 150, 200, or250 mg to an upper limit of 750, 1000, 1500, 2000, 2500, 3000, 4000,5000, or up to 10,000 mg. of the compositions described herein, or otherextracts of valerian. Preferred dosages for a 70 kg human are from about100, 200, or 250 mg to about 1000, 1500, 2000, or 2500 mg. These dosagescan be administered once, twice or up to four times per day, or two ormore dosages may be combined. The dose may also be tailored to achieve adesired effect, but will depend on such factors as weight, diet,concurrent medication and other factors which those skilled in themedical arts will recognize.

The present invention also encompasses pharmaceutical compositionscomprising a pharmaceutically acceptable carrier prepared for storageand subsequent administration, which have a pharmaceutically effectiveamount of the extract disclosed above in a pharmaceutically acceptablecarrier or diluent. Acceptable carriers or diluents for therapeutic useare well known in the pharmaceutical art, and are described, forexample, in Remington's Pharmaceutical Sciences (A. R. Gennaro edit.1985), Mack Publishing Co, Easton, Pa., or latest edition.Preservatives, stabilizers, dyes and even flavoring agents may beprovided in the pharmaceutical composition. For example, sodiumbenzoate, sorbic acid and esters of p-hydroxybenzoic acid may be addedas preservatives. In addition, antioxidants and suspending agents may beused.

These compositions may be formulated and used as, preferably, tablets,and also as capsules for oral administration. Suitable additionalexcipients are, for example, water, saline, dextrose, mannitol, lactose,lecithin, albumin, sodium glutamate, cysteine hydrochloride, and thelike. In addition, if desired, the pharmaceutical compositions maycontain relatively small amounts of nontoxic auxiliary substances, suchas wetting agents, pH buffering agents, and the like.

In practicing the compositions of the invention, the formulated dosagemay be used alone or in combination with other therapeutic or diagnosticagents. These products can be utilized in vivo, ordinarily in a mammal,preferably in a human, or in vitro. In employing them in vivo, theproducts or compositions can be administered to the mammal in any of avariety of manners known to persons skilled in the art, and may employany of a variety of dosage forms.

As will be appreciated by those of skill in the art, the methodsdescribed herein may be combined or complimented by other odor-reducingtechniques, such as those described in U.S. patent application Ser. No.60/173,983, Entitled “Process For Reducing The Odor Of Valeriana” filedon this date and herewith, the disclosure of which is herebyincorporated by reference herein.

EXAMPLE 1

An example of a Valerian tableting formulation for a tablet core isdescribed below and in Table 1.

TABLE 1 Concentration Commercial Ingredient (mg/tablet) Percent SourceValerian Extract 250.00 50.00 Described Herein Colloidal Silicon Dioxide1.50 0.30 Cabot Corp. (Cab-O-Sil), M5P Povidone K-30 30.00 6.00 ISPCroscarmellose Sodium, 10.00 2.00 FMC Corp. Type A Lactose Monohydrate204.50 40.90 Foremost Spraydried (Fast-flo 316) Magnesium Stearate 4.000.80 Mallinckrodt

The additional tablet components listed in Table 1 were weighed out and,if deemed necessary due to non-uniform consistency, as would beappreciated by those of skill in the art, milled individually to auniform consistency. First, dried valerian extract, prepared asdescribed herein, was milled through a 0.045″ round hole screen and putinto a blender. The colloidal silicon dioxide and a portion of thelactose monohydrate were hand-sieved through a #20 mesh screen. Thesewere combined with the dried Valerian extract in the blender and blendedfor approximately 10±2 minutes. Next, the croscarmellose sodium,Povidone K-30, and a second portion of lactose monohydrate were milledthrough a 0.045″ round-hole screen using a smooth impeller. Theaforementioned components were all combined and blended forapproximately 15±2 minutes. The magnesium stearate and the last portionof the lactose monohydrate were then hand-sieved through a #20 meshscreen and added to the powder blend. The components were then blendedfor an additional 3±1 minutes to achieve a mixture and sampled fortesting. The mixture was compressed into core tablets using amultiple-station tablet press and 0.4375″ round, plain, standard concavetooling and under the following conditions: tablet press speed, 60±5 rpm(mean table weight, 500±15 mg); mean tablet hardness, 8±2 Kp; meantablet thickness, 0.192±0.005″; tablet friability, <0.8%.

Once the core tablets were prepared, and not more than 24 hours beforeapplication, suspensions of the three coatings described in Tables 2-4,and the optional Opadry II coating (coatings 4, 6, 8 and 10 in FIG. 1),were individually and separately prepared.

EXAMPLE 2

An example of a composition of the first coating compartment (coating#1), as shown schematically as 4 in FIG. 1, is described below and inTable 2.

TABLE 2 Preferred Composition Example Ingredient % w/w Ingredient % w/wHydroxypropyl cellulose 10-70 Klucel EXF (Hercules, 50 or HydroxyethylAqualon Division) cellulose Hydroxypropyl  0-20 Methocel E4M Prem. 1methylcellulose (Dow Chemical) Plasticizer  0-20 Polyethylene Glycol8000 1 (Union Carbide) Anti-tackiness agent 20-60 Talc (Alphafil 500) 48(Luzanac America)

Water is the preferred solvent for the above example. Coating #1 wasprepared by adding hydroxypropyl methylcellulose to the initial portionof purified water and mixing for at least 20 minutes. Hydroxypropylcellulose was then dispersed into the solution and mixed for 5±1minutes. The mixing speed was then reduced and continued for at least 30minutes, then stopped for at least 60 minutes, a time sufficient todefoam. Mixing was then resumed and polyethylene glycol 8000 was addedand agitated for at least 15 minutes. Talc was then added and mixed forat least 15 minutes before coating application, and mixing continueduntil end of coating application.

EXAMPLE 3

An example of the composition of the second coating compartment (Coating#2), as shown schematically as 6 in FIG. 1, is described below and inTable 3.

TABLE 3 Preferred Composition Example Ingredient % w/w Ingredient % w/wSucrose 20-80 Sucrose (Domino Sugar 40 Corporation) Polyvinylpyrrolidone  0-30 Povidone K-30 (ISP) 10 Plasticizer  0-20 PolyethyleneGlycol 8000 8 Anti-tackiness agent  5-30 Colloidal Silicon dioxide 10(Cab-O-Sil), M5P (Cabot Corporation) Anti-tackiness agent  5-50 Talc(Alphafil 500) 32

The preferred solvent for the above example is water. Coating #2 wasprepared by adding polyethylene glycol 8000 to a second portion ofpurified water and mixing for at least 15 minutes. This was followed bythe addition of povidone K-30 and a mixing time of at least 15 minutes,sucrose and a mixing time of at least 10 minutes, colloidal siliconedioxide and a mixing time of at least 15 minutes before coatingapplication. As in Example 2, mixing continued until end of coatingapplication.

EXAMPLE 4

An example of the composition of the third coating compartment (Coating#3), as shown schematically as 8 in FIG. 1, is described below and inTable 4.

TABLE 4 Preferred Composition Example Ingredient % w/w Ingredient % w/wPolymethacrylate  1-30 Eudragit NE30D (Rohm)  9* Hydroxypropyl cellulose 5-70 Klucel EXF 40 Hydroxypropyl  0-20 Methocel E4M, Prem.  1methylcellulose Plasticizer  0-20 — — Anti-tackiness agent 10-70 Talc(Alphafil 500) 50 *Percent w/w of Eudragit NE30D refers to solid weightexcluding solvent

Water is the preferred solvent for the above example. Coating #3 wasprepared by first adding hydroxypropyl methylcellulose to the thirdportion of purified water and mixing for at least 20 minutes.Hydroxypropyl cellulose was then added and mixed for 5±1 minutes. Themixing speed was reduced and mixing was continued for at least 30minutes, then stopped for at least 60 minutes, a time sufficient todefoam. Mixing was then resumed and polyacrylate dispersion, 30%, andtalc were added and agitated for at least 15 minutes before coatingapplication. As in Examples 2 and 3, mixing continued until end ofcoating application.

The last solution, coating #4, was prepared by adding Opadry II to thefinal aliquot of purified water and mixing for at least 15 minutes athigh speed, then 15 minutes at a lower speed. Mixing was thenterminated.

15 kg of coating #1 was applied in 2 applications to a final targetweight gain of about 10% w/w of core tablet using parameters shown inTable 5:

TABLE 5 Conditions Target Coater (CompuLab-brand, 24 inch coating panThomas Engineering) Pan load 12.0 kg Gun to Bed Distance 5-11″ Inlet airflow 475 cfm Pan Speed 7 rpm Inlet air temperature 65° C. Outlet airtemperature 43° C. # of spray guns 2 spray rate/gun 20 g/min/gunAtomizing air pressure 40 psi pattern air 50 psi

The two-stage application allowed for a cleaning step of the coating panin the middle of the coating application which removed thecharacteristic odor from the pan and facilitated the odor-maskingfunction of the coating process.

10 kg of Coating #2 was applied to a target weight gain of about 10% w/wof core tablet using the same parameters as Coating #1, with theexception that the target pan load was 13.2 kg.

4.5 kg of Coating #3 was applied to a target weight gain of about 3% w/wof core tablet using the same parameters as Coating #2, with theexception that the target pan load was 14.4 kg and the pan speed was 8rpm.

Finally, 1.8 kg of Coating #4 (Opadry II) was applied to a target weightgain of about 3% w/w of core tablet using the same parameters as Coating#3, with the exception that the target pan load was 14.8 kg.

The tablets were dried between coating applications and sampled toensure a target mean weight. The mean tablet weights after completion ofcoatings #1-4 were 538-560 mg, 583-615 mg, 596-632 mg and 609-649 mg,respectively.

EXAMPLE 5 TABLET STABILITY

Valerian extract tablets having the composition described in Table 1 andcoated with the coating compartments described in Tables 2, 3, 4 and anouter, optional OpadryII (32K 11498) coating compartment were tested forlong-term stability under different storage conditions to monitorphysical integrity, seepage of the characteristic Valeriana odor andchemical integrity. The tablets were packaged as bulk (in polyethylenebags contained in fiber drums) and in blister cards with one tablet perblister. Samples of both were stored at 25° C./60% relative humidity andat 40° C./75% relative humidity.

The results of the stability testing for a period of six months aresummarized below in Tables 6 and 7, for tablets stored in standardblister cards and tablets stored in bulk, respectively. The resultsclearly indicate that the coating process, optimized to block thecharacteristic odor of valerian root extract, is stable both physicallyand chemically for a period of at least 6 months when stored either atnormal room conditions or at the condition of 40° C. and 75% relativehumidity, which one of skill in the art would expect to acceleratedegradation. Most importantly, the characteristic odor of valerian rootdoes not “seep out” of the composite coating, as it was not detected.Higher moisture content increases the hardness of the coating asevidenced by higher disintegration times (≦60 min at 6 months ascompared to ≦45 min initially) of the tablets stored in bulk (Seeespecially Table 7.).

TABLE 6 Stability of Tablets Stored in Blister Cards TIMEPOINT/CONDITION1 month 3 month 6 month 25°/60% RH 40°/75% RH 25°/60% RH 40°/75% RH25°/60% RH 40°/75% RH SPECIFI- replicate replicate replicate replicatereplicate replicate TEST CATION Initial 1 2 1 2 1 2 1 2 1 2 1 2 Total0.75-2.00 1.72 ± 1.7  1.7  1.7  1.7  1.7  1.7  1.6  1.7  1.7  1.7  1.7 1.7  Valerenic 0.05 Acids (mg/ tablet) Moisture ≦5% 3.88% 3.52 3.80 3.953.84 4.20 4.32 4.91 4.82 4.33 4.29 4.82 4.89 Content (%) Appear- round,round, no no no no no no no no no no no no ance, bi-convex, bi-convex,change change change change change change change change change changechange change Color, plain, plain, Odor green green color, color, coatedcoated tablets, tablets, odorless odorless Disinte- ≦45 min ≦45 min ≦45min ≦45 min ≦45 min ≦45 min ≦45 min ≦45 min gration

TABLE 7 Stability of Tablets Stored in Bulk TIMEPOINT/CONDITION 1 month3 month 6 month 25°/60% RH 40°/75% RH 25°/60% RH 40°/75% RH 25°/60% RH40°/75% RH SPECIFI- replicate replicate replicate replicate replicatereplicate TEST CATION Initial 1 2 1 2 1 2 1 2 1 2 1 2 Total 0.75-2.001.72 ± 1.7  1.7  1.7  1.7  1.7  1.7  1.8  1.7  1.7  1.7  1.7 1.7 Valerenic 0.05 Acids (mg/ tablet) Moisture ≦5% 3.88% 4.16 4.34 4.42 4.285.79 6.19 6.17 6.01 5.31 5.57 6.9 7.03 Content (%) Appear- round, round,no no no no no no no no no no no no ance, bi-convex, bi-convex, changechange change change change change change change change change changechange Color, plain, plain, Odor green green color, color, coated coatedtablets, tablets, odorless odorless Disinte- ≦45 min ≦45 min ≦45 min ≦45min ≦45 min ≦45 min ≦45 min ≦45 min gration

Although the present invention has been described in terms of certainpreferred embodiments, other embodiments which will be apparent to thoseof ordinary skill in the art in view of the disclosure herein are alsowithin the scope of the present invention. Accordingly, the scope of theinvention is intended to be defined only by reference to the appendedclaims.

The various articles of the scientific and/or medical literature, texts,and the U.S. and foreign patents and patent applications cited hereinare hereby incorporated by reference; each constitutes a part of thedisclosure of this specification. Furthermore, while specificembodiments, and working and prophetic examples of the invention havebeen described in detail to illustrate the broad applicability andprinciples underlying the invention, it will be understood by those ofskill in the art that the invention may be embodied otherwise withoutdeparting from such broad applicability and principles.

What is claimed is:
 1. A tablet comprising a pharmaceutically effectiveamount of an extract of the root of Valerian; and apharmaceutically-inert coating comprising one or more of the followingcoating compartments: a first coating compartment comprising ahydroxyalkyl cellulose wherein the alkyl group has between 1 and 10carbon atoms, and an anti-tackiness agent; a second coating compartmentcomprising a sugar and at least one anti-tackiness agent; and a thirdcoating compartment comprising a methacrylate copolymer, a hydroxyalkylcellulose and an anti-tackiness agent.
 2. The tablet of claim 1, whereinthe coating further comprising a coating compartment that is colored,flavored, or scented.
 3. The tablet of claim 1, wherein saidhydroxyalkyl cellulose is selected from the group consisting ofhydroxyethyl cellulose and hydroxypropyl cellulose.
 4. The tablet ofclaim 1, wherein said anti-tackiness agent is selected from the groupconsisting of talc, silicon dioxide, silica hydrogel, microcrystallinecellulose, alkali stearates, and starch.
 5. The tablet of claim 1,wherein said sugar is selected from the group consisting of sucrose,dextrose, dextrin, maltose, glucose, fructose, mannose, sorbitol,lactose, mannitol, and xylose.
 6. The tablet of claim 1, wherein saidmethacrylate copolymer is selected from the group consisting of themethacrylic acid copolymers, the aminoalkylmethacrylate copolymers, andthe ammoniomethacrylate copolymers.
 7. The tablet of claim 1, whereinsaid first coating compartment further comprises a compound whichfacilitates the coating process.
 8. The tablet of claim 1, wherein saidfirst coating compartment further comprises hydroxypropylmethylcellulose.
 9. The tablet of claim 1, wherein first coatingcompartment further comprises a plasticizer.
 10. The tablet of claim 9,wherein said plasticizer is selected from the group consisting ofpropylene glycol, glycerin, trimethylolpropane, polyethylene glycols,dibutyl sebacate, acetylated monoglycerides, diethylphthalate,triacetin, glyceryl triacetate, acetyltriethyl citrate and triethylcitrate.
 11. The tablet of claim 1, wherein said second coatingcompartment further comprises an agent which facilitates the coatingprocess.
 12. The tablet of claim 11, wherein said agent is selected fromthe group consisting of polyvinyl pyrrolidone, vinylpyrrolidone acetatecopolymer, vinyl acetate-crotonic acid copolymer, ethylacrylate-methacrylic acid copolymer, hydroxypropyl cellulose, gelatin,acacia, an ethylcellulose, and a methylcellulose.
 13. The tablet ofclaim 1, wherein said second coating compartment comprises aplasticizer.
 14. The tablet of claim 13, wherein said plasticizer isselected from the group consisting of propylene glycol, glycerin,trimethylolpropane, polyethylene glycols, dibutyl sebacate, acetylatedmonoglycerides, diethylphthalate, triacetin, glyceryl triacetate,acetyltriethyl citrate and triethyl citrate.
 15. The tablet of claim 1,wherein said second coating compartment comprises talc and a secondanti-tackiness agent.
 16. The tablet of claim 1, wherein said secondcoating compartment comprises silicon dioxide and a secondanti-tackiness agent.
 17. The tablet of claim 1, wherein said thirdcoating compartment further comprises hydroxypropylmethyl cellulose. 18.The tablet of claim 1, wherein said third coating compartment furthercomprises a plasticizer.
 19. The tablet of claim 18, wherein saidplasticizer is selected from the group consisting of propylene glycol,glycerin, trimethylolpropane, polyethylene glycols, dibutyl sebacate,acetylated monoglycerides, diethylphthalate, triacetin, glyceryltriacetate, acetyltriethyl citrate and triethyl citrate.
 20. The tabletof claim 1, wherein said third coating compartment comprises a watersoluble polymer or compound.
 21. The tablet of claim 20, wherein saidwater soluble polymer is selected from the group consisting ofhydroxypropyl cellulose, hydroxypropyl methylcellulose, acacia, sodiumcarboxymethylcellulose, dextrin, alginic acid, ethylcellulose resin,gelatin, guar gum, liquid glucose, methylcellulose, pregelatinizedstarch, sodium alginate, starch, zein, polyvinylpyrrolindone,vinylpyrrolidone-vinyl acetate copolymer, vinyl acetate-crotonic acidcopolymer and ethyl acrylate-methacrylic acid copolymer.
 22. A tabletcomprising a pharmaceutically effective amount of an extract of the rootof Valerian; and a pharmaceutically-inert coating comprising ahydroxyalkyl cellulose wherein the alkyl group is selected from thegroup consisting of methyl, ethyl and propyl groups.
 23. The tablet ofclaim 22, wherein the hydroxyalkyl cellulose serves to control therelease of the pharmaceutically effective amount of an extract of theroot of Valerian.
 24. A tablet comprising a pharmaceutically effectiveamount of an extract of the root of Valerian; and apharmaceutically-inert coating comprising at least one of the followingcoating compartments: a first coating compartment means for enhancingthe viscosity of the extract; a second coating compartment means forenhancing the palatability of the tablet; and a third coatingcompartment means for effecting controlled release of the extract. 25.The tablet of claim 22, wherein the hydroxyalkyl cellulose ishydroxypropyl methylcellulose.
 26. The tablet of claim 22, wherein thecoating further comprises a colorant.
 27. The tablet of claim 22,wherein the coating further comprises a scent.
 28. The tablet of claim22, wherein the coating further comprises a flavoring agent.